This invention is directed to touch fastening, and particularly to bi-stable touch fasteners (e.g., hook and loop fasteners) and articles incorporating such fasteners.
A number of fastening systems, such as diaper fastening systems, incorporate a hook and loop system for easy fastening and release. The hook component typically includes a flat plastic sheet laminate with a number of protruding hooks that engage with a number of loops protruding from a corresponding loop component. The flat hook backing remains essentially flat while undergoing engagement with the corresponding loop component. Such hook and loop fastening systems rely primarily on shear forces that resist unfastening. The force of the user allows the hooks to engage into corresponding loops, with little dimensional change in either the hook component or the loop component. More particularly, the hook component and the loop component tend to remain flat, or bent only about a single axis, throughout the engagement process.
Since the shear forces resist unfastening of the hook and loop fastening system, hook and loop components are typically separated from one another using peel forces. However, with little resistance to the peel forces, the hook and loop fastening system is susceptible to coming unfastened at unexpected, and often undesirable, times.
There is a need or desire for a hook and loop fastening system with improved fastening security.
The present invention is directed to a touch fastening system with improved fastening security. The improved fastening security is attributable to a design that utilizes the forces used to apply a product and the three-dimensional geometry of corresponding hook components and loop components.
According to one aspect of the invention, a touch fastener comprises a hook component and a loop component, with each of the hook and loop components having exposed elements on an active side thereof for releasable engagement with the exposed elements of the other component. The active side of one of the hook and loop components has a surface that bi-stabilizes between a first stable form for initiating engagement with the active side of the other of the hook and loop components, and a stable, concave form for securing an initiated engagement of the other of the hook and loop components. The other of the hook and loop components has a flexible backing adapted to conform to the concave form of the one of the hook and loop components during engagement.
In some embodiments, the bi-stabilizing surface is inherently either semi-spherical or semi-ellipsoidal in its stable concave form.
In presently preferred forms, the exposed elements of the hook component comprise hooks, each hook having a free end with an engageable head. Preferably, the heads of at least two adjacent hooks are farther apart from one another when the bi-stabilizing surface is in its first stable form than when the bi-stabilizing surface is in its stable, concave form. Ideally, the heads of at least two adjacent hooks contact one another when the bi-stabilizing surface is in its stable, concave form.
The exposed elements of the hook component comprise, for some applications, mushroom-shaped hooks. These mushroom-shaped hooks may have flat upper surfaces, for example.
In some cases the bi-stabilizing surface is of the hook component.
According to another aspect, a touch fastener comprises a hook component and a loop component, with each of the hook and loop components having exposed elements on an active side thereof for releasable engagement with the exposed elements of the other component. The active side of one of the hook and loop components has a surface that bi-stabilizes between a first stable form for initiating engagement with the active side of the other of the hook and loop components, and a stable, concave form for securing an initiated engagement of the other of the hook and loop components. The exposed elements of the hook component comprise hooks, and the heads of at least two adjacent hooks contact one another when the bi-stabilizing surface is in its stable, concave form, to secure engaged loop component elements.
According to another aspect, a touch fastener comprises a pair of releasably engageable components, each of the components having exposed elements on an active side thereof for releasable engagement with the exposed elements of the other component. The active side of one of the components comprising a surface that bi-stabilizes between a first stable form for initiating engagement with the active side of the other of the components, and a stable, concave form for securing an initiated engagement of the other of the components. The exposed elements of at least one of the components comprise mushroom-shaped hooks.
In some preferred instances, the exposed elements of one of the components comprise fibers exposed for engagement by the hooks. In other cases, the exposed elements of both of the components comprise arrays of self-engageable mushroom-shaped hooks.
The above-described touch fastener systems are employed to advantage in various articles. In one aspect of the invention, an absorbent article (e.g., a diaper, a feminine hygiene product, or an incontinence product) has the featured touch fastener arranged to secure the absorbent article. Preferably, the touch fastener is arranged to extend over an underlying, curved surface of a wearer""s body with the bi-stabilizing surface in its stable, concave form, for conforming the touch fastener to the wearer. In other aspects of the invention, the fastener system is provided on a training pant or medical garment.
According to yet another aspect of the invention, a method of releasably securing an article over an underlying curved surface is provided. The method includes grasping one of a pair of touch fastener components secured to the article, the grasped component having an active side comprising a surface that bi-stabilizes between a first stable form for initiating engagement with an active side of the other of the pair of touch fastener components, and a stable, concave form for securing an initiated engagement of the other of the touch fastener components. With the surface of the grasped component in its first stable form, an active side of the other component is contacted with the active side of the grasped component. With the active sides of the components in contact, the bi-stabilizing surface of the grasped component is forced or made to toggle to its stable, concave form to secure the components in engagement and to conform the grasped touch fastener component to the underlying curved surface.
In some instances, the article comprises a garment (e.g., a diaper) and the underlying curved surface is of a wearer""s body.
According to yet other aspects of the invention, methods are provided for forming the bi-stable fastener products as herein described.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.